Gineolata agus Gineòlas Cèitean

Nuclear & Cytoplasmic Genetics

• Tha genetic material of all living things, bacteria and eukaryotes is DNA (deoxyribonucleic acid)
• DNA is also genetic material in many viruses that infect both bacteria and eukaryotes
• Some viruses have RNA (ribonucleic acid) as their genetic material.
• Eukaryotes have DNA mainly within the nucleus
• DNA in the nucleus is complexed with protein and is organized into linear structures called chromosomes.
• Chromosomes are visible under microscopes after staining.
• Each eukaryotic chromosome has a single DNA molecule from one end to the other.
• Bacterial DNA is usually organized into a single circular chromosome with few associated proteins.
• Chromosomes consist of two chromatids connected by a primary constriction (centromere) or kinetochore
• The kinetochore is a protein structure located at the centromere, which is involved in chromosome movement during cell division.
• The ends of the chromosomes are called telomeres.
• Chromosomes contain chromonemata that have granules called chromomeres carrying genetic material.

List of Contents

• Chromosomes: Page 1
• The Life cycle: Page 8
• Cell division: Page 10
• Chemical composition of DNA: Page 21
• Chromosome aberrations: Page 33

Chromosomes and Cell Division

• Genetic material, both prokaryotes and eukaryotes, is DNA.
• Prokaryotes' genetic material is usually within the cell, while eukaryotes have most of their genetic material within the nucleus.
• Chromosomes are made up of a single molecule of DNA.
• The position of the centromere varies among chromosomes
• Telomeres are the ends of the chromosome

Types of Chromosomes

• Metacentric: The centromere is in the middle, producing arms of nearly equal length, and they appear V-shaped during anaphase.
• Submetacentric: The centromere is situated closer to the middle, creating arms of unequal length.
• Subtelocentric: The centromere is close to one end, producing one long arm and one short arm
• Telocentric: The centromere is located at the end of the chromosome, which consist of a single arm.

Giant Chromosomes

• In certain tissues of some organisms, chromosomes may be significantly larger than typical chromosomes.
• Examples of these giant chromosomes include lampbrush chromosomes found in vertebrate oocytes and polytene chromosomes found in Drosophila salivary glands.

Polytene Chromosomes

• These chromosomes are much larger and thicker than normal chromosomes.
• They are found in the salivary glands of fruit flies (Drosophila).
• The DNA replicates repeatedly without the chromosome dividing, creating multiple copies of the same DNA molecule.
• The resulting chromosome has many identical DNA strands lying side-by-side.

Lampbrush Chromosomes

• These types of giant chromosomes are found in the oocytes of many vertebrate species, including amphibians, reptiles, fish, and birds.
• They are considerably larger than typical chromosomes.
• These chromosomes are characterized by a main axis made of four chromatids, which form many loops consisting of RNA and proteins along their lateral sides.

The Cell Cycle

• Cells grow and undergo division in a cyclical process called the cell cycle.
• The cell cycle involves three key stages: G1, S, and G2, collectively called interphase.
• Mitosis is when the cell divides its chromosomes and DNA

Cell Division (Mitosis)

• Mitosis is a process of cell duplication where the nucleus of a cell divides into two identical nuclei.
• It involves four phases: prophase, metaphase, anaphase, and telophase

Meiosis

• Meiosis is the process of cell division involved in sexual reproduction.
• There are two consecutive divisions during meiosis, these are called meiosis I and meiosis II.
• The chromosome number is reduced by half during this process.
• Meiosis produces four daughter cells.
• Meiosis results in genetic variation due to recombination through crossing-over.
• Meiosis I and Meiosis II stages are comprised of Prophase, Metaphase, Anaphase and Telophase stages.

Chemical Composition of DNA

• DNA is made up of nucleotides.
• Each nucleotide is composed of a phosphate group, a five-carbon sugar, and a cyclic nitrogenous base.
• The sugar in DNA is deoxyribose
• The DNA bases are adenine (A), guanine (G), thymine (T), and cytosine (C).
• Adenine pairs with thymine, and guanine pairs with cytosine.
• DNA is usually found as a double helix.

DNA Double Helix

• Watson and Crick discovered the DNA double-helix structure in 1953.

Chromosome Aberrations

• Chromosomal aberrations are structural changes in chromosomes.
• They can occur spontaneously or be induced by factors like radiation or chemicals.
• The changes can involve deletion, duplication, inversion, and translocation.

Polyploidy

• Polyploidy happens when an organism has more than two complete sets of chromosomes.
• Types include autopolyploids (same genomes duplicated) and allopolyploids (different genomes).
• Polyploidy is common in plants but less frequent in animals, often causing increased size or vitality.

Aneuploidy

• Aneuploidy describes a condition where a cell or organism has an abnormal number of chromosomes, not a multiple of the haploid number for that species.
• This can happen due to errors during meiosis and result in monosomy, nullosomy, trisomy, or tetrasomy.

Cytoplasmic Transmission

• Cytoplasmic traits are passed on through the maternal lineage and are not influenced by the paternal lineage.
• These traits are encoded in the DNA of different organelles like mitochondria and chloroplasts
• Chloroplasts possess larger genomes than mitochondria.